The present invention relates to an inductor, transformer, choke coil or similar wire wound electronic component.
A wire wound electronic component has been put to practical use in various forms, and various improvements have been made in the past. Japanese Utility Model Laid-Open Publication No. 51-115547, for example, teaches a fixed inductance device having a bobbin made up of a core and flanges, conductive layers formed on the circumferential surfaces of the flanges, and a coil wound round the core. A conductor protruding from opposite stripped ends of the coil is connected to the conductive layers and to conductive portions provided on a printed circuit board. Japanese Utility Model Laid-Open Publication No. 56-110612 discloses an inductance device having flanges formed with grooves, and a coil whose conductor is received in the grooves at both ends thereof.
Japanese Patent Laid-Open Publication No. 57-73916 proposes a miniature inductor including a core, flanges formed at both ends of the core, conductive layers respectively formed on the flanges, and a coil wound round the center of the core. In this inductor, electrodes are formed after the assembly has been sealed with a resin. Further, Japanese Utility Mode Laid-Open Publication No. 61-144616 discloses a chip coil in which a conductor protruding from opposite stripped ends of a coil is drawn out via grooves formed in rectangular flanges, and electrodes are also formed on the sides of the flanges.
As stated above, a wire wound electronic component has a coil wound round a core and has a conductor protruding from the coil bonded to the electrodes of flanges. Such a wire wound electronic component may be produced by a method shown in FIG. 27. As shown in FIG. 27, (A), in a section, a bobbin having a core 900 and flanges 902 formed at both ends of the bobbin 900 is prepared. Then, as shown in FIG. 27, (B), electrodes 904 are respectively formed on the sides and end faces of the flanges 902 by dipping or similar technology. Subsequently, as shown in FIG. 27, (C), a coil 906 is wound round the core 900 and has its outgoing conductor 908 connected to the electrodes 904 by, e.g., heat pressure welding.
As shown in FIG. 27, (D), a resin or a paint is applied to the core portion, which was wound the coil 906, in order to form a coating or armor 910. Then, as shown in FIG. 27, (E), a plating 912 of, e.g., Ni is formed on each electrode 904. Finally, as shown in FIG. 27, (F), the assembly is entirely trimmed into a column having a rectangular cross-section.
In parallel with advances in the small size, light weight configuration of an electronic apparatus, there is an increasing demand for small size, light weight wire wound electronic components. In addition, improvements in mounting efficiency and productivity are essential from the cost saving standpoint. It is an object of the present invention to reduce the size and weight of a wire wound type electronic component without degrading its performance or reliability. It is another object of the present invention to improve the mounting efficiency and productivity of a wire wound electronic component.
A wire wound electronic component of the present invention is characterized by comprising a bobbin including a core and flanges formed at both ends of the core, electrodes respectively formed on the flanges, a coil wound round the core and having stripped portions thereof connected to the electrodes, and a coating formed on the coil and having a flat surface.
Also, a method of producing a wire wound electronic component of the present invention comprises the steps of machining a block for forming a bobbin having a core and flanges, forming electrodes on the flanges, winding a coil round the core and connecting stripped portions of the coil to the electrodes, and providing a coating having a flat surface on the coil.